unzOpenCurrentFile3() always returns zero for method and level

Noticed this little difference between minizip's compatibility interface and the original minizip API:

In unzOpenCurrentFile3() the returned method and level values are always zeroes. For method this is just an inconvenience (because it can be retrieved by unzGetCurrentFileInfo64()), but level is important because there is no other way to retrieve it from an existing .zip. The correct level is useful when re-creating an existing entry in raw mode, to make it as much identical to the original as possible.

Return method and level from unzOpenCurrentFile3. #289

Fixed returning compression method. #289

That should fix it. Let me know if you have any issues.

Thank you so much! I can confirm your patches fixed the issue. But... it lead to another one, which luckily seems like a trivial fix: zipOpenNewFileInZip5() resets the received level parameter to zero in raw mode. Vs. original minizip, which leaves it as is, making it possible to control this for raw entries. Fix seems simple:

diff --git a/mz_compat.c b/mz_compat.c
index aaf4885658..567dd97cbd 100644
--- a/mz_compat.c
+++ b/mz_compat.c
@@ -185,8 +185,10 @@ extern int ZEXPORT zipOpenNewFileInZip5(zipFile file, const char *filename, cons
         file_info.aes_version = MZ_AES_VERSION;
 #endif
 
+#if 0
     if (raw)
         level = 0;
+#endif
 
     return mz_zip_entry_write_open(compat->handle, &file_info, (int16_t)level, password);
 }

Opened a PR with (a finalized version of) the above: #291

Thanks! I have merged it. Are you using this to delete entries in a zip?

Entry deletion is a major "user" of raw mode and there is a high-level wrapper I'm maintaining that's doing just that. I'm not using entry deletion though. My use-case is creating backups while reusing unchanged entries from the previous backup. It can be a nice time saver [0]. (I used to use the command-line zip tool for that, but had to reimplement it from scratch to deal with encrypted input files.)

[0] Though I'm evaluating a performance drop here just now on a particular system. Not sure where to look yet.

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unzOpenCurrentFile3() always returns zero for `method` and `level` #289

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unzOpenCurrentFile3() always returns zero for method and level #289

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nmoinvaz commented on Jul 27, 2018

vszakats commented on Jul 27, 2018

vszakats commented on Jul 27, 2018

nmoinvaz commented on Jul 27, 2018

vszakats commented on Jul 27, 2018

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unzOpenCurrentFile3() always returns zero for `method` and `level` #289